Field of the Invention
The present invention relates to coaxial jack interconnection devices, and more particularly to a coaxial jack having a shielded center conductor and an internal switch mechanism.
Type 440 coaxial jacks, which are compatible with type 440 plugs, are known generally for use in telephone cross-connect systems. One such system, known as System III DSX-3/4, has been used in telecommunication networks in the United States. System III DSX-3/4 is used to manually cross-connect DS3, STS1, STS3 or DS4 level signals manually at a central office.
System III DSX-3/4 includes a DSX-3/4 module into which is housed a 3-inch by 3-inch by 0.5 inch die cast metal case, that includes a set of five type 440 jacks. Three mechanical switches are interposed between four of the jacks. The switches have activators and contacts that enter side openings in the jack barrels to sense an inserted plug. See, e.g., U.S. Pat. No. 4,815,104 (March 1989). The five type 440 jacks open on a front panel of the case, and two bulk head type BNC jacks are mounted on a rear panel of the case. Other components inside the case include two hand-soldered coaxial cables, a metal housing for the five type 440 jacks, three resisters, and one inductor. The case is often referred to as a 1201A jack set.
In U.S. Pat. No. 5,882,217, a coaxial jack having an internal switch mechanism is provided that facilitates the incorporation of a printed wiring board to form a DSX-3 module. Another cross-connect system, the DIXI-3, has been used in telecommunication networks. The DIXI-3 system is used to interconnect and cross-connect DS3, STS1 and STS3 signals manually in a central office. The DIXI-3 system includes a DIXI-3 module that is housed in a 0.75-inch by 5.5-inch by 6.0-inch plastic case. The DIXI-3 case houses a printed wiring board with eight right-angle BNC connectors. Because the DIXI-3 system is a rear-cabled, rear cross-connected system, four BNC connectors are located at a rear end of the module and four BNC connectors are located at a front end of the module. The BNC connectors at the rear are for cabling and cross-connecting operations, and the BNC connectors at the front are for patching and monitoring. Migration from the earlier mentioned DSX-3 system with type 440 jacks to a DIXI-3 system may be simplified by substitution of the type 440 jacks provided in U.S. Pat. No. 5,882,217 for the aforementioned BNC jacks, for patching and monitoring on the DIXI-3 modules.
Prior art type 440 coaxial jacks, such as that disclosed in U.S. Pat. No. 5,882,217, with an internal switch assembly, can sustain transmission rates as high as 55 Mb/s. However, above this rate the presence of unshielded regions in the jack may significantly degrade the transmission performance of the device. In particular, the unshielded contact mating area of such prior art coaxial jacks may be the source of significant deterioration of the transmitted signal. This is because the center conductor of the jack is in close proximity to the normally opened and common contacts of the switch assembly. Such switch assemblies and contacts have not, heretofore, been adequately electrically isolated from the center conductor to provide for transmission rates above 55 Mb/s. Thus, there is a need for a type 440 coaxial jack that is either straight mount or right-angled, having an internal switch, and which includes a center conductor that is electrically isolated from an associated switching mechanism.